The main objective of the research set forth in this proposal is to gain a better understanding of the factors capable of inhibiting or preventing drug use. The proposed study will proceed on two levels. On a theoretical level, this research is designed to test an hypothetical model of the factors promoting or inhibiting the use of tobacco, alcohol, and marijuana as well as to determine the relative importance of teachers and peers as influence sources. On a practical level, this research will test the efficacy of a comprehensive psychosocial substance abuse prevention strategy when implemented by teachers or peer leaders. Six schools (N equals 1200) will be randomly assigned to the following conditions: (1) teacher administered intervention, (2) peer administered intervention, (3) teacher administered intervention plus maintenance, (4) peer administered intervention plus maintenance, (5) pretest-multiple posttest control, and (6) pretest-single posttest control. The intervention consists of a 20 session multi-component program which focuses on the key personal factors facilitating the onset of tobacco, alcohol, and marijuana use according to an hypothetical model similar to that developed by Jessor and his colleages to explain problem behavior. The major components include a cognitive component, a decision-making component, a relaxation training component, a social skills training component, and a self improvement component. Our earlier work with a similar intervention strategy has demonstrated its short-term effectiveness for preventing the onset of cigarette smoking. The proposed research will not only provide important information concerning the determinants of drug use, but will provide a test of a strategy for intervening on those factors and inhibiting or preventing drug use.